For only the second or third time in my life, I was in a Prada store, but I wasn't buying anything. And none of the staff seemed to mind; they smiled knowingly as I looked at everything but the shoes and suits. I walked up the ramps covered in thick, cream carpet and looked out of the diamond-shaped glass "bubbles" which made the views of Tokyo's Omotesando district change with every step. The Prada building is just as spectacular from the outside, like a comet-sized diamond embedded at an angle in the ground. From the top floor, you can see the new 250m-long mall built around spiral walkways that go deep underground and the glass Dior store, like an eight-storey jellyfish.

Omotesando is also home to the cult clothing line Bathing Ape, the epicentre of Tokyo's youth culture. Armies of kids covered in its bright camouflage and shiny trainers wander round the four Bathing Ape stores all day and often camp out overnight on a rumour that a new top or trainer has just arrived. They get their hair cut at the Bape salon and eat off gold-rimmed china, especially made with the Ape logo, at the Bape cafe.

The clothes look like streetwear but are made to the standards of a designer label. Everything is so bling that Bathing Ape has become the label of choice for some of America's biggest rappers. Pharrell Williams has even started a clothing range called Billionaire Boys Club designed and made by Bathing Ape's founder, Nigo. The likes of Jay-Z, Gwen Stefani and Beyoncé are also looking to Tokyo for inspiration. Architects and designers have been doing the same for years, but the endorsement of such mainstream heavyweights might mean that a new generation will soon start heading out to Tokyo. The day I arrived, Vanity Fair was in town to interview Nigo, and I'd only just missed Natalie Portman and Stella McCartney, who both took him out for dinner.

Omotesando is one of the swankier areas of Tokyo, but I thought I'd stumbled into the posh part of town half a dozen times before I realised that most of Tokyo looks like the posh part of any other city. I didn't see an area that looked like it needed a good clean, let alone a slum, which is some achievement for one of the most populated cities on the planet.

Just behind Omotesando, the Maisen restaurant is famous for its tonkatsu - deep fried pork cutlet with rice and cabbage. Normally this is an everyday dish, cooked up in minutes, but at Maisen they've been obsessively tweaking and improving the recipe for years, coming up with three perfect sauces which draw people from all over the country. The restaurant is in an old bathhouse with high ceilings, thick wooden benches and even some of the original signs telling bathers where to undress. For a national institution, it wasn't expensive, and lunch for two came to about £12.

That night, we drank beer from chilled gold goblets in the Piano bar, one of hundreds on the backstreets of Shinjuku, a city within the city that looks likes five or six Times Squares squeezed together. The bar can't have been much larger than a hundred square feet, spread over two floors. We squeezed up a staircase so narrow that my shoulders touched the red velvet walls as I walked up. The waiter stayed downstairs unless we rang a glass bell, leaving us alone with a till, surrounded by shelves of expensive glassware and oil paintings.

The days of paying ludicrous prices for tiny capsules are long gone. Even so affordable hotels are often far from the centre and have small rooms. At the Andon Ryokan, I covered the entire floor of my room when I rolled out the mattress. The boutique b Akasaka hotel is much closer to central Tokyo and although the rooms are only slightly bigger, they are so packed with brilliant gadgets that I didn't mind. The free broadband connection actually worked and the heated toilet seats had built-in bidets which, as AA Gill put it, leave you questioning your sexuality. I came to see Tokyo in the same way as I saw the b Akasaka: a huge playground of such bright ideas and fantastic design that I barely noticed how cramped it could be. I was too busy being amazed and thinking "why haven't we got these? Why haven't we thought of this?!"

And if this was the basic, minimum standard hotel, what must luxury be like? Within minutes of checking in at the Mandarin Oriental, I was lying in a Jacuzzi, inches away from a floor-to-ceiling window 37 floors up, feeling like Nero. Shinjuku was perfectly framed above the water and looked even more like another city. Get a room on the other side of the building and, if it's a clear day when you wake up, you can open the curtains (by pressing the button next to your bed, naturally) and find a view of mount Fuji.

I asked the concierge to recommend a good traditional Japanese restaurant and was directed to Zakuro, a basement within walking distance that I would never have found on my own. By the time we finished, we could barely speak, the food was so good. When we left, seven waitresses gathered to say goodbye, and one came up on to the street and waved until we were out of sight. Almost anywhere else, this might have felt like a cynical ploy to attract future business. But I experienced so much goodwill in Japan I'm sure it was genuine. Porters refused tips and a taxi driver turned the meter off when roadworks slowed us down.

The trip made such an impression on me that I've developed a prejudice in favour of anything that comes from Japan. I've even had the urge to go up to Japanese people on the streets of London and say, "I know, I've been there. No one else knows how to do anything."

Weird but wonderful

Bisty's Jingumae Hidden halfway down the subterranean slopes of the Tadao Ando-designed Omotesando Hills, Bisty's offers the conveyor-belt sushi approach to wine tasting and buying - it's all self-service. You prepay, fill your own glass, and nary a snotty sommelier in sight.·bistys.jp, 03-5771-4466.

Heaven's If designer furniture and laid-back music is your bag, Heaven's cafe might be just the ticket. In the thick of Ebisu, where Tokyoites too cool for Shibuya go. ·cafe-heavens.com, 03-5428-3399.

Sign in Gaienmae Brought to you by the same design team that created Tokyo's best boutique hotel, Claska, Sign cafe and bar is home to inspired pop design that lives up to every preconceived notion about Neo-Tokyo. The coffee's not bad either. ·transit-web.com/01/0102, 03-5474-5040.

Granbell Hotel More pop art is on offer at Shibuya's latest boutique hotel, where the restaurant, Plate of Pies, serves, well, you can guess. ·granbellhotel.jp.

Maid cafes Take a tour of Akihabara (Manga territory) and you'll soon come across a Maid cafe where the waitresses dress up in sexy maid outfits. In the name of equality, there are now butler cafes for women where customers are greeted at the door with "Welcome, Your Highness."

Harajuku Centre of Japan's most extreme fashion, where teenagers engage in cosplay (costume play), dressed as Lolitas etc. Eulogised in song by Gwen Stefani as 'a subculture in a kaleidoscope of fashion'.